Born in Berlin on 25 April 1904, Franz Hübner completed his apprenticeship as a plumber and joined the German Communist Party (KPD) in 1923. As “opponent steward” (“Gegner-Obmann”) for the Red Front Fighters’ Alliance, he had the task of keeping tabs on the activities of the SA, through which he came in contact with SA members. In 1933 Franz Hübner worked as a custodian of a house in Schöneberg. He was taken to the SA Prison Papestrasse in March 1933. Here it is believed that he divulged information about Max Bilecki, among others, who was then arrested and died as a result of severe torture. Hübner also denounced his property manager, the communist Alfred Rosenbaum, and his son Gerhard. Gerhard Rosenbaum suffered fatal injuries caused by maltreatment in the SA Prison. In 1949 Franz Hübner was sentenced to twelve years imprisonment for “crimes against humanity”, four years of which were remitted.